1. Field of the Invention
The present invention relates to a cannula for dispensing fluid products, particularly for vaginal and rectal applications.
2. Description of the Related Art
Cannulas are known for dispensing medical fluid products which are used, in particular, for vaginal and rectal applications and which are generally sold in packs together with tubes or bottles containing the fluid products.
The known cannulas are composed of a cylinder suitable for containing the product and inside which is a piston integral with the extremity of a push rod.
The cylinder has an open extremity that can be coupled with the dispenser mouth of the tube, to introduce the quantity of product to be applied into the cylinder, and through which the introduced product is dispensed.
The opposite extremity of the cylinder is closed by a bottom wall which has a hole, through which the push rod is inserted for slide movement within the cylinder. The bottom wall acts as a piston stop element to prevent its withdrawal.
The dispensing of the product introduced into the cannula occurs by moving the push rod, to slide the piston towards the open extremity of the cylinder.
These known cannulas have a number of drawbacks. To illustrate they are rather complex in terms of structure and assembly and that, being for hygienic reasons of the single-use type and requiring a push rod for each cylinder, they produce a considerable waste of materials.
To overcome such drawbacks, cannulas are known composed of one cylinder, which has the opposite extremities open and inside which a piston is fitted in a sliding manner, and a push rod, separate from the piston, is removably coupled to same.
At the opposite extremities of the cylinder undercuts or stop shoulders are obtained or formed for stopping the sliding of the piston and preventing the piston from coming out of the cylinder as a result of the action of the push rod.
These latter cannulas can be sold in packs containing a single push rod, a plurality of empty single-use cylinders to be used for the different applications, and one or more product tubes.
In this case, one of the two extremities of the cylinders can be coupled with the dispenser mouth of the tube for the introduction of the product into the cylinders, while the opposite extremity acts as a passage for the push rod.
These latter known cannulas have made it possible to curb the consumption of materials, for the same push rod, in fact, can be used with a plurality of cylinders.
Nevertheless, these cannulas are not without drawbacks as well, tied above all, to the need to use one or more tubes of product to load the cylinders before use.
To overcome this drawback, an alternative type of so-called “pre-filled” cannula is known, wherein the cylinder, at the time of purchase, is already filled with the product to be applied and which has closing caps, at the two opposite extremities which are removed at the time of use.
The pre-filled cannulas are not without drawbacks however, for they are of a rather complex construction, and they have rather high production costs and production cycles.
The cylinders, the pistons, the push rods and the closing caps in fact are normally made by molding polymer materials, in several pieces (at least five), separate from one another and subsequently assembled. This involves the design and building of various molds and laborious assembly operations which negatively affect the production costs and times of the cannulas, as well as producing considerable and costly material waste.
From the patent WO 2004/014476 on the other hand a particular type of pre-filled cannula is known in which the cylinder and the piston are made in a single body piece and, at an extremity of the cylinder, are joined together along a connection line with tearable weakened section.
The opposite extremity of the cylinder is closed by means of a tear-off film.
This particular type of pre-filled cannula also has a number of drawbacks. For example the fabrication of the piston in a single body piece with the cylinder is considerably complicated and hard to achieve in practice.
It should also be considered that big difficulties of a practical-manufacturing nature are encountered because of the use of the tear-off film.
Another type of pre-filled cannula is on the other hand known from EP 1 518 574 and comprises a push rod that can be extended by means of a telescopic rod system between a retracted configuration and an elongated configuration.
The push rod is made in a retracted configuration together with the cylinder at an extremity of same.
The opposite extremity of the cylinder is closed by a cover cap made to fit over the cylinder permanently along its entire length until it joins at the base of the push rod.
The cannula or cylinder described in EP 1 518 574 also suffers various drawbacks. The push rod involves the manufacture and the assembly of a plurality of telescopic elements, with consequent increase in time and costs of designing, producing and assembly, as well as the waste of a considerable quantity of materials.